Exhaust muffler for internal combustion engines

ABSTRACT

An exhaust muffler for internal combustion engines adapted to receive exhaust gases from exhaust ports of internal combustion engines. The muffler comprising a hollow body having a peripheral edge adjacent to which a flexible diaphragm is resiliently supported to allow exhaust gas to escape between the peripheral edge of the body and an adjacent side of the diaphragm; the diaphragm being provided with resilient means for adjusting said diaphragm and tending to hold the diaphragm toward said peripheral edge of the body portion of the muffler and in substantially contiguous relationship therewith whereby exhaust forces internally of said body deflect the diaphragm structure away from the peripheral edge of the body and allow exhaust gases to escape between the peripheral edge and the diaphragm.

United States Patent 1 1 Rhodes l l EXHAUST MUFFLER FOR INTERNAL COMBUSTION ENGINES [76] Inventor: William A. Rhodes, 4421 N, 13th Pl., Phoenix. Ariz. 85014 [22] Filed: Apr. 19, 1974 [21] Appl. No: 462,359

[52] US. Cl. 181/64 A; 181/40 [51] Int. Cl. FOln 1/16 [58] Field of Search .1 181/36 A, 40, 47 A. 64 A. 181/64 B, 65. 63, 64 R [56] References Cited UNITED STATES PATENTS 1,927,947 9/1933 Newell 181/47 A UX 2.419664 4/1947 Tabbertwn... 181/64 B UX 3,318,412 5/1967 Bailey 181/40 X 3.379178 4/1968 Skowron 181/36 A UX 3.67.5,732 7/1972 Rosen et al. N 181/40 X 3,688,869 9/1972 Murphy 181/41) 1 1 Aug. 5, 1975 Primary E.\mnim'r--.l0seph W. Hartary Ass-Lima! E.\'amincrJohn F. Gonzales 1571 ABSTRACT An exhaust muffler for internal combustion engines adapted to receive exhaust gases from exhaust ports of internal combustion engines. The muffler comprising a hollow body having a peripheral edge adjacent to which a flexible diaphragm is resiliently supported to allow exhaust gas to escape between the peripheral edge of the body and an adjacent side of the diaphragm; the diaphragm being provided with resilient means for adjusting said diaphragm and tending to hold the diaphragm toward said peripheral edge of the body portion of the muffler and in substantially contiguous relationship therewith whereby exhaust forces internally of said body deflect the diaphragm structure away from the peripheral edge of the body and allow exhaust gases to escape between the peripheral edge and the diaphragm.

9 Claims. 5 Drawing Figures EXHAUST MUFFLER FOR INTERNAL COMBUSTION ENGINES BACKGROUND OF THE INVENTION A great many exhaust gas muffler structures have been devised for the purpose of muffling the noises transmitted from the exhaust ports of internal combustion engines and it is well known that many of the exhaust gas noise muffling devices have created substantial back pressure communicating with exhaust ports of internal combustion engines, and have, thereby, re duced the performance or power output of such en gines due to such back pressure. Additionally, it has been very difficult to efficiently muffle or silence the exhaust gas noises from conventional two-cycle engines due to the exhaust and induction characteristics of such engines which rely substantially upon the flow of exhaust gases from the exhaust ports to cause a scavenging or partial induction force tending to aspirate or draw flesh fuel into the respective combustion chamber above the piston at a time when the exhaust gases are passing from the exhaust port of the engine. The convention mufflers used on two-cycle engines have either limited power output of such engines or have been quite inefficient relative to the muffling of exhaust gas noises.

The foregoing problems have been particularly noticeable in small engines such as model aircraft engines which are basically light-weight, two-cycle engines.

These small engines which operate in a range of to thousand revolutions per minute create a great amount of noise and have been particularly annoying in populated areas.

Heretofore the various attempts at muffling exhaust gas noises from model aircraft engines have been quite futile due to the space requirements as well as the weight requirements, and also due to the characteristics of the small two-cycle engines.

SUMMARY OF THE INVENTION The present invention relates to an exhaust gas noise muffler comprising an hollow body having an open end with a peripheral edge surrounding the open end and a diaphragm resiliently urged to lie in close proximity and tending to engage the peripheral edge so that exhaust gases must pass between said peripheral edge and the diaphragm. The diaphragm is resiliently adjustable so as to provide for adjustment of tension to hold the diaphragm at one side thereof toward and in contiguous relation with the peripheral edge of the muffler body which surrounds the open end thereof hereinbefore set forth.

The hollow muffler body, inwardly of the diaphragm and beyond the exhaust port of the respective engine, has sufficient cubic displacement to be substantially greater than the swept volume displacement of engine cylinder as for example, the invention has been operated with remarkably good results when the cubic dis placement of the space in the muffler body ranges be tween two and a half to five relative to one with respect to the swept volume displacement of the engine cylinder. The exhaust gas noise muffler of the invention, with its adjustable diaphragm, provides for a novel method of tuning the muffler to the exhaust gas flow and noise emission of a particular engine v This method comprises the operation of the engine at a optimum high speed which may be at an RPM range in which the engine develops its highest torque and with the engine operating at such speed the diaphragm of the muffler is resiliently adjusted toward the open end of the muffler and into resiliently loaded relation to the edge of the open end of the body. This adjustment being continued until the RPM is slightly reduced due to back pressure of the exhaust gases and then the adjustment on the diaphragm is slightly relaxed allowing a reduction in exhaust gas pressure until the engine again returns to the aforementioned high speed RPM at which it is operating at an optimum such as full torque or other optimum characteristic. At this particular adjustment point of the diaphragm, the exhaust gas noise level will be at the lowest possible attentuation in accordance with the operation of the invention.

The diaphragm may be made of a stack of resilient metal discs such as steel or beryllium copper and as an alternative, a rubber-like disc backed by a metal disc may be used where the rubber disc is contiguous with the peripheral edge of the muffler body at its open end.

Means is provided for coupling the body directly to the side of an engine cylinder in communication with an exhaust port of the engine so that exhaust gases travel directly from the engine cylinder port into the interior of the muffler body. Additionally, the muffler of the invention may be installed remotely from the cn gine and connected by a conventional head pipe.

Accordingly, it is an object of the present invention to provide an exhaust gas noise muffler for internal combustion engines having characteristics superior to other mufflers, particularly for use in connection with various internal combustion engines and including twocycle engines.

Another object of the invention is to provide an exhaust gas noise muffler for internal combustion engines which is very efficient in attenuating noise while, at the same time, causing no appreciable loss in engine performance.

Another object of the invention is to provide a very simple, light-weight and compact exhaust gas noise muffler for internal combustion engines such as the small two-cycle engines used in model aircraft.

Another object of the invention is to provide an exhaust gas noise muffler for internal combustion engines which affords a novel method for tuning a muffler to an internal combustion engine exhaust system wherein the engine is run at an optimum high speed while the muffler is adjusted so that the diaphragm of the muffler at its one side is adjusted toward and in contiguous relationship with a peripheral edge at the open end of the body of the muffler and where such adjustment is con tinued until RPM of the engine reduces slightly, then the adjustment is reversed until back pressure is reduced to a point where the RPM of the engine is resumed so that noise attentuation is accomplished without appreciably affecting the performance of the engine.

Further objects and advantages of the invention may be apparent for the following specification, appended claims and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of the exhaust gas noise muffler for internal combustions in accordance with the present invention;

FIG. 2 is a view of the opposite side of the muffler from that as shown in FIG. I;

FIG. 3 is a sectional view taken from the line 3-3 of FIG. 2;

FIG. 4 is an exploded view of the parts of the muffler of the invention; and

FIG. 5 is a view ofthe muffler of the invention shown connected to a conventional head pipe and remote from an exhaust gas port of an internal combustion engine.

DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIGS. 1, 2 and 3 of the drawings, the muffler of the invention is provided with a hollow body I0 which is generally cup-shaped and cylinderical in form; it being understood that even though the body shown in FIG. 2 is generally circular in shape, that a rectangular or elongated, hollow body structure may be an obvious form which can be used for accomplishing the basic functions of the invention as will be hereinafter described.

The body is provided with an open end 12 shown best in FIGS. 2 and 3 of the drawings. This open end 12 is provided with a peripheral edge 14 and opposite to the open end 12 is a substantially closed side 16 having an exhaust gas inlet opening 18 which straddles a central fixture 20 integral with the closed side 16. The closed 16 is provided with a pair of bolt receiving open ings 22 and 24, shown best in FIG. 4 of the drawings, through which bolts 26 are extended and screw threaded into corresponding screw-threaded holes 28 in the engine block 30 at opposite sides of an exhaust gas port 32 from which exhaust gases are exhausted by the engine when in operation.

The fixture 20, as shown in FIG. 3, is provided with a screw-threaded rod 34 having an internally screwthreaded nut 36 adjustably mounted thereon.

A diaphragm assembly 38 is comprised of a plurality of resilient semirigid discs 40 as shown best in FIG. 4 of the drawings and these discs are provided with central openings 42 fitted over the rod 34 and the nut 36 is adjusted against the stack of plates 40 to hold the assembly 38 in close proximity to the peripheral edge 14 of the body 10.

It will be understood that the plates or discs 40 are of substantially resilient material such as steel or beryllium copper any other suitable material, and for small engines these discs may be 0.010 inches in thickness as an example, The nut 36 on the rod 34 may be adjusted until the inner-most disc or plate 40 is contiguous with the peripheral edge 14 of the body so that exhaust gases must deflect the stack of discs away from the peripheral edge [4 in order to allow exhaust gases to pass from the port 32 and out of body [0 and between the peripheral edge 14 and an inner-most side 44 of the diaphragm assembly 38. As shown in FIG. 4 of the drawings. a conventional washer 46 may be disposed between the nut 36 and the outer most one of the plates or discs 40.

An alternate form ofthe invention may comprise one of the discs 40 and a relatively thick rubber-like disc 48 having one side 50 to which the disc 40 is contiguous and an opposite side 52 corresponding to the inner side 44 of the assembly 38 as shown in FIG. 3 of the drawings. Thus the rubber-like disc 48 may be adjusted into contiguous relationship to the peripheral edge 14 to function in a manner as hereinbefore described.

In operation the engine 30 is started and the diaphragm of the invention is adjusted so that it is adapted to provide clearance between the peripheral edge 14 and the inner side 44 of the diaphragm assembly 38 so that exahust gases may readily pass from the chamber area 54 between the peripheral edge 14 and the inner side 44 of the diaphragm assembly 38. The engine is operated at a high RPM which may be an optimum torque speed for the engine. The nut 36 is tightened so as to provide tension of the plates 40 of the diaphragm assembly 38 until the inner side 44 of the assembly 38 is in such close proximity to the peripheral edge I4 that RPM of the engine is slightly reduced. whereupon the nut 36 is turned in the opposite direction to relax the tension of the diaphragm assembly 38 and to relieve back pressure so that exhaust gases may flow freely between the edge 14 and inner side 44 of the diaphragm assembly 38. The nut 36 being adjusted until the engine again returns to its maximum optimum RPM, at which point the engine performance is not seriously or appreciably compromised. while exhaust gas noise muffling is attained.

It has been found that mufflers according to the present invention operate most efficiently when the displacement of the chamber area 54 is substantially greater than the volume displacement of the cylinder of the engine 30. As for example, a ratio of five to one of the cavity 54 and engine displacement respectively produces very good results in accordance with the present invention.

In the modification as shown in FIG. 5 of the drawings, a head pipe 56 conducts gas from an engine exhaust port and into a housing 58 similar to the body 10. The housing 58 having a peripheral edge 60 at its open end similar to the edge I4 shown in FIG. 2 of the draw' ings. A nut 62 adjustably holds a diaphragm assembly 64 which is similar to the diaphragm assembly 38 hereinbefore described. Accordingly, it will be appreciated that the muffler of the invention may be operated remotely from the exhaust port area such as the exhaust port 32 of the engine 30.

It will be seen from the drawings, that a small model aircraft engine may be equipped with the muffler structure of the invention coupled directly to the engine in a very compact manner so that the entire exhaust system may be a very light-weight structure and therefore compatible with small, lightweight engines in model airplanes of the like.

It will be obvious to those skilled in the art that the shape of the body 10 may be varied. It may be circular, rectangular or elongated and may have one or more threaded rods 34 and adjusting nuts 36 and may be used directly on the side of a multiple port engine, or may be used remotely as disclosed in FIG. 5 of the drawings.

It will be obvious to those skilled in the art that various modifications may be resorted to without departing from the spirit of the invention,

I claim:

1. An exhaust muffler for internal combustion engines comprising: a generally hollow body having an open end; said body having a peripheral edge at said open end; said peripheral edge surrounding said open end; fixture means connected to said body; said fixture means having a diaphragm support inwardly of said peripheral edge; a diaphragm supported on said diaphragm support; said diaphragm having a freely deflectable side surface portion extending from said support and overlying the entire area of said peripheral edge and disposed in close proximity thereto whereby exhaust gasses under pressure in said body may pass outward between said entire edge and said side surface portion; and adjustable means on said diaphragm support for adjusting the spaced relationship of said side surface portion relative to said peripheral edge.

2. The invention as defined in claim I wherein said adjustable means comprises a screw threaded rod portion extending through said diaphragm. and a nut screw threaded on said rod portion and bearing against said diaphragm in opposition to gas pressure on said side surface portion; said nut being adjustably moveable on said rod to thereby apply force tending to force said diaphragm against said peripheral edge portion of said body.

3. The invention as defined in claim 1 wherein said diaphragm is of substantially resilient material.

4. The invention as defined in claim 2 wherein said diaphragm is of substantially resilient material.

5. The invention as defined in claim 1 wherein said body is provided with openings adapted to correspond with the exhaust port structure of an internal combustion engines; and screw threaded means adapted to clamp said body in contiguous relation with said engine to receive exhaust gas from the exhaust port means thereof.

6. The invention as defined in claim 5 wherein said engine is a two-cycle engine and said body is clamped to the exhaust port area thereof.

7. An exhaust muffler for internal combustion engines comprisings; a generally hollow body having an open end; said body having a peripheral edge at said open end; said peripheral edge surrounding said open end; fixture means connected to said body; said fixture means having a diaphragm support aligned generally with a central area of said open end; a diaphragm supported on said diaphragm support; said disphragm having a side surface portion extending from said support and overlying said peripheral edge and disposed in close proximity thereto whereby exhaust gasses under pressure in said body may pass outward between said edge and said side surface portion, sand diaphragm is composed of a pluarlity of substantially contiguous semirigid resilient metal plates.

8. An exhaust muffler for internal combustion engines comprisings; a generally hollow body having an open end; said body having a peripheral edge at said open end; said peripheral edge surrounding said open end; fixture means connected to said body; said fixture means having a diaphragm support aligned generally with a central area of said open end; a diaphragm supported on said diaphragm support; said diaphragm having a side surface portion extending from said support and overlying said peripheral edge and disposed in close proximity thereto whereby exhaust gasses under pressure in said body may pass outward between said edge and said side surface portion; said diaphragm comprises a metal plate held by said fixture means; and a resilient rubber-like diaphragm portion disposed between said plate and said peripheral edge of said body.

9. An exhaust muffler for internal combustion engines comprisings; a generally hollow body having an open end; said body having a peripheral edge at said open end; said peripheral edge surrounding said open end; fixture means connected to said body; said fixture means having a diaphragm support aligned generally with a central area of said open end; a diaphragm supported on said diaphragm support; said diaphragm having a side surface portion extending from said support and overlying said peripheral edge and disposed in close proximity thereto whereby exhaust gasses under pressure in said body may pass outward between said edge and said side surface portion; said diaphragm comprises resilient yieldable means tending to hold said diaphragm against said edge at the open end of said body. 

1. An exhaust muffler for internal combustion engines comprising: a generally hollow body having an open end; said body having a peripheral edge at said open end; said peripheral edge surrounding said open end; fixture means connected to said body; said fixture means having a diaphragm support inwardly of said peripheral edge; a diaphragm supported on said diaphragm support; said diaphragm having a freely deflectable side surface portion extending from said support and overlying the entire area of said peripheral edge and disposed in close proximity thereto whereby exhaust gasses under pressure in said body may pass outward between said entire edge and said side surface portion; and adjustable means on said diaphragm support for adjusting the spaced relationship of said side surface portion relative to said peripheral edge.
 2. The invention as defined in claim 1 wherein said adjustable means comprises a screw threaded rod portion extending through said diaphragm; and a nut screw threaded on said rod portion and bearing against said diaphragm in opposition to gas pressure on said side surface portion; said nut being adjustably moveable on said rod to thereby apply force tending to force said diaphragm against said peripheral edge portion of said body.
 3. The invention as defined in claim 1 wherein said diaphragm is of substantially resilient material.
 4. The invention as defined in claim 2 wherein said diaphragm is of substantially resilient material.
 5. The invention as defined in claim 1 wherein said body is provided with openings adapted to correspond with the exhaust port structure of an internal combustion engines; and screw threaded means adapted to clamp said body in contiguous relation with said engine to receive exhaust gas from the exhaust port means thereof.
 6. The invention as defined in claim 5 wherein said engine is a two-cycle engine and said body is clamped to the exhaust port area thereof.
 7. An exhaust muFfler for internal combustion engines comprisings; a generally hollow body having an open end; said body having a peripheral edge at said open end; said peripheral edge surrounding said open end; fixture means connected to said body; said fixture means having a diaphragm support aligned generally with a central area of said open end; a diaphragm supported on said diaphragm support; said disphragm having a side surface portion extending from said support and overlying said peripheral edge and disposed in close proximity thereto whereby exhaust gasses under pressure in said body may pass outward between said edge and said side surface portion, sand diaphragm is composed of a pluarlity of substantially contiguous semirigid resilient metal plates.
 8. An exhaust muffler for internal combustion engines comprisings; a generally hollow body having an open end; said body having a peripheral edge at said open end; said peripheral edge surrounding said open end; fixture means connected to said body; said fixture means having a diaphragm support aligned generally with a central area of said open end; a diaphragm supported on said diaphragm support; said diaphragm having a side surface portion extending from said support and overlying said peripheral edge and disposed in close proximity thereto whereby exhaust gasses under pressure in said body may pass outward between said edge and said side surface portion; said diaphragm comprises a metal plate held by said fixture means; and a resilient rubber-like diaphragm portion disposed between said plate and said peripheral edge of said body.
 9. An exhaust muffler for internal combustion engines comprisings; a generally hollow body having an open end; said body having a peripheral edge at said open end; said peripheral edge surrounding said open end; fixture means connected to said body; said fixture means having a diaphragm support aligned generally with a central area of said open end; a diaphragm supported on said diaphragm support; said diaphragm having a side surface portion extending from said support and overlying said peripheral edge and disposed in close proximity thereto whereby exhaust gasses under pressure in said body may pass outward between said edge and said side surface portion; said diaphragm comprises resilient yieldable means tending to hold said diaphragm against said edge at the open end of said body. 